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From their data, Abrahamczyk and Renner estimate that the oldest South American groups are approximately 15 million years old, while the oldest North American hummingbirds appeared around 6 million years ago. In both regions, the oldest hummingbird groups are those that pollinate the oldest bird-pollinated plant groups, strongly supporting the idea that they evolved together.
Notably though, in both regions the build up of plant species diversity was gradual. In general, once a plant group becomes adapted to hummingbird pollination there is not a huge amount of subsequent diversification. So while hummingbirds have certainly had some impact on plant evolution, it is less than might have been expected from such a lengthy and close relationship. Why is this so?
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The researchers doubt this is merely due to the relatively recent evolution of the hummingbird-plant relationship. As they point out, the much older South American groups are no more species rich than the younger North American hummingbird-plant groups. One explanation put forward by the researchers is that bird pollinators can cover much greater distances than insect pollinators, increasing gene flow between plant populations and preventing the fragmentation of populations that drives speciation.
Secondly, they speculate that it might be evolutionary inadvisable for a hummingbird to focus on a single plant species. Indeed, many hummingbirds pollinate several related plant species; for example, the North American ruby-throated hummingbird pollinates three different species of the Silene family.
This is quite different from the plant-pollinator relationship in many insect pollinated plants, where one insect species is often a specialist pollinator of just one plant species, a relationship likely to lead to further speciation. Conversely, the promiscuity of hummingbirds discourages both bird and plant from evolving further specialised adaptations, resulting in less species diversity than we might otherwise see.
The deep evolutionary relationship of hummingbirds and the plants they pollinate cannot be doubted; one could not exist without the other. Yet this new research suggests that in a certain sense the relationship is a stagnant one; without the promise of greater fidelity, plants will only change so much to accommodate their partners.
View the latest posts on the BMC Series blog homepage. A justified title with the interesting post, its all about hummingbirds and their relationship with the plants. Thanks for sharing this important piece of information with us. Although the mice lose weight, the activity of the genes in the fat tissue is similar to that of the mice that continue to eat as much as they want. In addition, the fat composition in old mice does not change as much as in young mice. Usually, reduced food intake leads to increased formation of mitochondria in fatty tissue.
But the study showed that this is no longer the case when older mice are switched to a lower calorie diet. This inability to change at the genetic and metabolic levels may contribute to the shortened lifespan of these animals.
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Does having children make us live longer? The numbers say yes, but the reasons are not yet understood. Large dataset shows that income, work status and education have a clear influence on mortality in Germany. Researchers can determine the disease vulnerability of older people using a defined set of substances in the blood. The evolution of short lifespan in African killifish is explained by the lack of strong selection against deleterious mutations. All cells in the body have the basic ability to protect themselves from infection, called the innate immune response.
But how cells do this is not very well understood. Recently, scientists from the Max Planck Institute for Biology of Ageing and the University of Cologne, found that the size of the nucleolus plays an important role in protecting cells against infection. Official retirement age is not the only factor that determines the duration of our working life.
Scientists discover that nucleolar size correlates with health and lifespan in organisms as diverse as roundworms, flies and humans. Maintaining a normal weight, not smoking, and drinking alcohol at moderatel levels add healthy years to life.
The life expectancy of older fish is extended if their gut is colonized with the microorganisms of younger fish. In mice, dietary restrictions can lead to changes in lipid metabolism, thus increasing the animals' lifespans.
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